The number of DNA molecules and chromatids in a chromosome at metaphase stage is respectively ?

Options

A. 1 and 1
B. 2 and 1
C. 2 and 2
D. 1 and 2

Answer

To solve the question about the number of DNA molecules and chromatids in a chromosome at the metaphase stage, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Metaphase Stage**:
- Metaphase is a stage in cell division (specifically in mitosis) where chromosomes are aligned at the cell's equatorial plane. This stage follows prophase and is crucial for ensuring that chromosomes are properly segregated into daughter cells.

2. **Recall DNA Replication**:
- Prior to metaphase, during the S phase of interphase, DNA replication occurs. Each chromosome is duplicated, resulting in two identical copies known as sister chromatids.

3. **Identify Chromosome Structure**:
- At metaphase, each chromosome consists of two sister chromatids. Therefore, each chromosome can be considered as a chromatid pair.

4. **Determine the Number of DNA Molecules**:
- Each sister chromatid contains one DNA molecule. Since there are two sister chromatids in a chromosome, this means there are two DNA molecules per chromosome.

5. **Determine the Number of Chromatids**:
- As established, each chromosome at metaphase consists of two sister chromatids. Thus, the number of chromatids in a chromosome at this stage is also two.

6. **Conclude the Answer**:
- Therefore, at the metaphase stage, the number of DNA molecules is 2, and the number of chromatids is also 2.

### Final Answer:
- The number of DNA molecules and chromatids in a chromosome at the metaphase stage is respectively **2 and 2**.